Differential hydraulic cylinder mechanism

ABSTRACT

A STATIONARY PISTON OF FORMING A LOAD SUPPORTING COLUMN SLIDABLY AND ROTATABLY MOUNTS A CYLINDER ASSEMBLY TO ENCLOSE FLUID PRESSURE CHAMBERS ON OPPOSITE SIDES OF A PISTON, FLUID UNDER PRESSURE IS SUPPLIED TO THE PRESSURE CHAMBERS THROUGH CONDUITS EXTENDING THROUGH THE PISTON ROD IN ORDER TO ELEVATE OR LOWER THE CYLINDER ASSEMBLY SUPPORTING A LOAD.

@Qt. 2-6, 1911 R. B. MCCREERY 27,204

DIFFERENTIAL HYDRAULIC CYLINDER MEoEANIsM Original Filed May 4., 1965 2Sheets-Sheet 1 78 /55 Robert B. McCreery 2 /52 IN VEN TOR.

Oct. 26, 1911 R. B. M CREERY DIFFERENTIAL HYDRAULIC CYLINDER MECHANISM 2Sheets-Sheet 8 Original Filed May 1, 1965 Rober/ B.Mc6reery INVENTOR;

United States Patent 27,204 DIFFERENTIAL HYDRAULIC CYLINDER MECHANISMRobert B. MeCreery, P.O. Box 157, Xenia, Ohio 45385 Original No.3,181,436, dated May 4, 1965, Ser. No. 165,761, Jan. 12, 1962.Application for reissue May 1, 1967, Ser. No. 641,060

Int. Cl. Ftllb /02 US. Cl. 92117 14 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISLOSURE A stationary piston rod forming a loadsupporting column slidably and rotatably mounts a cylinder assembly toenclose fluid pressure chambers on opposite sides of a piston. Fluidunder pressure is supplied to the pressure chambers through conduitsextending through the piston rod in order to elevate or lower thecylinder assembly supporting a load.

This invention relates to a fluid pressure operated load handlingmechanism of the differential pressure type and constitutes animprovement over the load handling mechanism disclosed in my priorcopending application Serial No. 89,980, filed February 17, 1961, nowPatent No. 3,134,231.

The differential pressure operating mechanism of the present inventionlike that disclosed in my aforementioned copending application, involvesthe use of large diameter columns more easily installed by means of topand bottom adapter plates to floor or ceiling ofany structure, tothereby form a fixed structural member eliminating the necessity forauxiliary guides. The differential pressure operating mechanismfurthermore involves a differential pressure displaced cylinder assemblyslidably mounted on the column structure by widely spaced bearings so asto insure low bearing loads and in connection with the large diameter ofthe column structure to endow the differential pressure operatingmechanism with a large eccentric load capacity. Furthermore, thepressure cavities defined within the cylinder assembly are of reducedvolume requiring smaller volume of oil and consequently more rapidoperating speed in axially displacing the eccentrically loaded cylinderassembly which is also capable of being rotated 360. The construction ofthe differential pressure operated mechanism of the present invention inaddition to the aforementioned attributes, provides additionaladvantages in connection with bearing load capacity, accessibility forservicing and enables the manufacture of component parts with increasedeconomy. The mechanism of the present invention furthermore permits theassembly of a unit mechanism in accordance with a greater variety ofdesign requirements from comparatively smaller numbers of standard sizedvariations in the component parts of a mechanism unit.

It is therefore a primary object of the present invention to provide adifferential pressure operating mechanism utilizing an inner steppeddiameter column structure cooperating with an outer cylinder assembly todefine annular pressure cavities within which differential pressureforces are generated by introduction of fluid of any suitable typeincluding oil in order to axially displace the cylinder assembly in amore rapid manner by virtue of the reduced volume of the pressurecavities so defined between the step diameter column and the cylinderassembly.

Another obpect of this invention is to provide a differential pressureoperated eccentric load handling mech- Reissued Oct. 26, 1971 anism withwhich fluid handling equipment may be more efficiently associated byvirtue of the fact that no flexible hose connections are required inorder to accommodate movement of the outer cylinder assembly andfurthermore optional mounting space is provided interiorly of themechanism for the components of the fluid handling system associatedwith the pressure operated load handling mechanism.

An additional obpect of this invention involves improved facilities fordismantling the outer cylinder assembly without disassembly of theinstallation of the mechanism enabling replacement of bearingassemblies, repair of component parts of the cylinder assembly andinspection of the slide bearing surfaces on the inner column assembly.

A further object of this invention is to provide a differential pressureoperated load handling mechanism the sliding surfaces of which areformed externally 0n portions of the columnassembly renderingmanufacture of the mechanism parts more economical since precisionmachining and finishing of outside diameters is easier than internalsurfaces and further facilitating the inspection and maintenance of suchsurfaces.

A still further object of the present invention in accordance with theforegoing objects, is to provide a cylinder assembly slidably supportedby an inner column assembly at three different spaced locations axiallythereof so as to provide greater design flexibility with respect toeccentric loads to be handled and also providing for the attachment toand modification of the outer cylinder assembly without adverselyaffecting internal clearances and dimensions in a manner to adverselyaffect operation of the mechanism because of distortion and denting ofthe cylinder assembly.

In accordance with the foregoing object, the cylinder assembly of thepresent invention is formed from a number of sections by virtue of whicha wider variety of different cylinder lengths are made available from arelatively limited number of standard size sections in order to meetdesired spacing of bearings in accordance with eccentric loading andcylinder stroke.

Additional objects of the present invention include the formation of theinner supporting column assembly from a pair of differential diameterend portions interconnected by an enlarged diameter center section, theselection of standard diameter sizes for the column end portions withinlimits fixed by the center section diameter capable of more flexiblyaccommodating actuating force and fluid volume requirements.

The foregoing invention also embodies all of the advantages set forthwith respect to the aforementioned copending application including theWide variety of load handling installations with which the mechanism maybe associated.

These together with other objects and advantages which will becomesubsequent apparent reside in the details of construction and operationas more fully hereinafter described and claimed, reference being had tothe accompanying drawings forming a part hereof, wherein like numeralsrefer to like parts throughout, and in which:

FIGURE 1 is a perspective view of a typical differential pressureoperated load handling mechanism unit of the present invention.

FIGURE 2 is a longitudinal side elevatio-nal view of the pressureoperated mechanism unit with parts broken away and shown in section.

FIGURE 3 is a perspective view of the inner supporting column assemblyof the pressure operated mechanism with parts broken away and shown insection,

FIGURE 4 is a sectional view taken substantially through a planeindicated by section line 44 in FIG- URE 2.

FIGURE 5 is a partial sectional view of a modified orm of cylinderassembly.

FIGURE 6 is a partial sectional view of a further modication of thecylinder assembly.

FIGURE 7 is a longitudinal side elevational view with arts broken awayand shown in section of another form f pressure operated mechanism.

FIGURE *8 is a partial sectional view taken through a lane indicated bysection line 8 8 in FIGURE 7 illus- "ating a still further modificationof the cylinder asembly as illustrated in FIGURE 2.

Referring now to the drawings in detail, the pressure perated mechanismof the present invention involves an ssembled unit generally referred toby reference numeral 0 in FIGURE I mounted for example between ananhoring floor 12 and ceiling 14. An inner column as- :mbly 1'6 axiallyprojecting beyond both ends of an outer ylinder or tubular housingassembly 1 8 is therefore anhored to the floor and ceiling by suitableadapter anchor evices or mounting brackets depending upon theinstallaon. An eccentric load schematically referred to by refrencenumeral 20 is therefore attached by any load suport m eans in anysuitable manner to the outer cylinder ssembly 18 for displacement withthe cylinder assembly long the inner column assembly 16. Reference to myrior copending application aforementioned, will indicate 1e wide varietyof installational arrangements with which 1ch unit or combination ofunits may be associated tcluding load elevators for trucks. Also, thesignificance nd advantages arising from the particular installationrounting facilities and load carrying facilities of the unit 0 willbecome apparent.

Referring now to FIGURE 2 in particular, it will be bserved that theinner supporting or guide column as- :mbly 16 includes a central sectiongenerally referred to y reference numeral 22 constituting a piston towhich a nall diameter end portion 24 is connected at one axial ad whilethe large diameter end portion 26 is connected the other axial end ofthe center section 22. The center action is therefore formed by acylindrical wall member 8 the external surface of which is precisionmachined nd finished to define a sliding bearing surface 30. End latemembers 32 and 34 are welded to the opposite axial ads of thecylindrical wall member 28 toenclose a chamer 36 therewithin. The smalldiameter end portion 24 of re column assembly is co-axially positionedwith respect a the center section 22 by means of the end plate member 2and welded thereto. The end portion 24 is also formed f a cylindricalwall member 38 having an end closure lember 40 welded thereto and a headmember 42 welded the cylindrical wall member 38 adjacent to but spacedcm the opposite axial end to define a fluid passage space 4 togetherwith the end plate member 32 of the center :ction 22. The cylindricalwall member 38 is provided 'ith fluid passages or apertures 46 incommunication with re passage space 44 for cooperation with the fluidhanling facilities to be described hereafter. The end portion 4 alsodefines a chamber '48 between the enclosure memer 40 and the head member42. Similarly connected in )axial alignment with the center section 22,is the large iameter end portion 26 including a cylindrical wall memer50 having welded thereto adjacent one axial end, the aclosure member 52and adjacent the opposite axial end 1e head member 54. A passage space56 is also formed etween the head member 54 and the end plate member 4of the center section which space 56- is in fluid comrunication withapertures 58. The cylindrical wall memers 38 and 50 of the end portionsthus form external caring surfaces of different diameter for cooperationwith re spaced slide bearings of the cylinder assembly 18. lowever, thecolumn assembly 16 itself is independently lounted at the desiredlocation as shown in FIGURE 3 ad forms a guide column or a stationarypiston rod in :ldition to its other functions in connection with thefluid perated mechanism unit 10.

The cylinder assembly 18 is axially slidable with respect to the columnassembly and is also rotatable without restriction thereabout. Thecylinder assembly however is assembled from separate components theaxial lengths of which may be varied in accordance with the desiredspacings of the bearings along the sliding surfaces of the columnassembly in accordance with cylinder stroke or eccentric load capacity.The cylinder assembly is thus formed of a pair of outer casing sections60 and 62 of variable length respectively defining pressure differentialcavities 64 and 66 about the column assembly. The volumes of thepressure cavities 64 and 66 will therefore be determined by the axiallengths of the outer casing sections 60 and 62 and the diameters of theend portions of the column assembly. The outer casing section 62therefore tapers radially inwardly for connection by welding to an endslide bearing assembly '68 which includes a hearing mounting sleeve 70to which the outer casing 62 is welded, the sleeve 70 internallymounting a sleeve bearing 72 spaced from fluid wiping packing 74maintained assembly within the sleeve 70 by a gland 76 secured byfastener 78 to the sleeve 70* and covered by the gland ring 80.Associated with the other outer casing section 60, is an end bearingassembly 82 of a diameter reduced with respect to the end bearingassembly 68 for engagement .with the sliding bearing surface of thesmall diameter portion 24 of the column assembly. The end bearingassembly 82 therefore also includes a mounting sleeve 84 interiorlymounting a bearing sleeve 86 spaced from the packing 88 which ismaintained assembled by the gland 90 secured to the sleeve by thefasteners 92 and covered by the gland ring 94. The end bearing assembly82 is however not directly connected to the outer casing section 60which is uniform in diameter throughout its length unlike the casingsection 62. Instead, the casing section 60 is interconnected to itsassociated end bearing assembly 8-2- by a pressure head member 96respectively welded to the end bearing sleeve 84 and to the casingsection 60 interiorly thereof. The cylinder assembly is completed by theinterconnection of the outer casing sections 60 and 62 to each other inaxially spaced relation by the dynamic slide hearing assembly generallyreferred to by reference numeral 98.

The slide bearing assembly '98 not only facilitates the assembly anddisassembly of the cylinder 18 without requiring removal of the innercolumn assembly but also provides an intermediate slide bearing betweenthe end bearing assemblies 68 and 82. The slide bearing assembly 98furthermore maintains the pressure cavities 64 and 66 in fluid tightrelation to each other. The slide bearing assembly 98: thereforeincludes a pair of axially aligned mounting sleeves 100 and 102 whichrespectively mount interiorly thereof for contact with the slide bearingsurface 30 of the center section, bearing sleeves 1104 and fluid wipingpacking 106. A leakage preventing clamping structure generally referredto by reference numeral 108 maintains the packing 106 in assembledspaced relation. The clamping structure 108 as more clearly seen inFIGURES 2 and 4, includes clamping flanges 110 and 112 spaced from eachother by an annular portion of a gland 114 in engagement with theexternal surface of the center section 22, said clamping flanges beingsecured to each other by means of cap screws 116 that extend alsothrough the gland member 114. The clamping structure 108 of the bearingassembly 98 therefore not only permits easy dismantling of the cylinderassembly without disassembly of the column structure, but also maintainsthe pressure cavities 64 and 66 in fluid tight relation to each other.Thus to replace a leaky packing, the fastening bolts 116 are removed soas to merely separate the mounting sleeves 100 and 102 for removal ofthe packing gland .114 and packings 106 for example, without requiringany further dissassembly of parts. FIGURE 5 illustrates a modi fied formof bearing assembly wherein the bearing mounting sleeves 118 and 120 arein abutting relation to each other and are internally recessed forreceiving therebetween the gland member 122. Abutting flanges 124 and126 are respectively welded to the mounting sleeve members 118 and 120for clamping said sleeve members to each other by means of cap screws.FIGURE 6 illustrates a further modification of the clamping structurewherein the bearing mounting sleeve members 128 and 130 are grooved notonly to receive therebetween the gland member 122 as described withrespect to FIGURE but also for interfitting relation to each otherassuring thereby axial alignment. The sleeve members 128 and 130therefore are respectively formed with annular recesses 132 and 134 forsuch purpose. Abutting clamping flanges 136 and 138 are therefore alsowelded to the abutting ends of the sleeve members 128 and 130 and areprovided with cap screws for securing them together. FIGURE 8illustrates a still further modification wherein the mounting sleevemembers 140 and 142 are secured to each other by threaded engagementbetween threaded portions 144 and 146 of the sleeve members. The fluidwiping packings 148 are spaced from each other in this latterarrangement by the gland member 150 disposed in axial alignment with thethreaded portions of the sleeve member.

It will be observed from FIGURES 2, 3 and 4, that a pair of fluidhandling feeder pipes 152 and 154 extend through the chamber 156 of thelarger diameter end portion 26 of the column assembly and are welded tothe enclosure member 52 and end plate member 54-. The fluid handlingconduit 154 therefore provides fluid communication with a fluid handlingsystem exterior to the pressure operated mechanism [and] through aconduit connected thereto as shown by dotted line in FIG- URE 2 forcontrolling the flow of hydraulic fluid to the annular pressure chamber66 through the passage space 56 and aperture 58. The fluid handlingfeeder conduit 152 on the other hand provides fluid communicationbetween [an] the exterior fluid handling system associated with the unit10 and the differential pressure actuating cavity 64 through the passagespace 44 and aperture 46. The conduit 154 therefore also extends throughthe chamber 36 of the center section 22 and is also welded to the endplate members 32 and 34 thereof. From the foregoing description, it willbe appreciated that fluid under increasing pressure supplied by theconduit 152 to the pressure cavity 64 will react between the axial endof the bearing mounting sleeve 100 and the pressure head member 96tending to displace the cylinder assembly in an upward direction withrespect to the column assembly as viewed in FIGURE 2. Fluid pressure mayat the same time exist within the chamber 66 equalizing the pressure onthe slide bearing assembly 98 without developing however the displacingdifferential force in view of the substantially equal end surfaces ofthe mounting sleeve member 102 andv bearing sleeve member 70 definingthe opposite axial ends of the annual pressure cavity 66. The conduit154 may therefore simultaneously exhaust the fluid from the cavity 66 asthe cylinder assembly is displaced upwardly by an increasing pressure offluid generated by the fluid handling system associated with thepressure operated mechanism unit 10. Controlled venting of the pressureWithin the pressure cavities through the conduits 1'52 and 154 maythereby provide for load controlled movement of the cylinder assembly ina downward direction as viewed in FIGURE 2. Although the conduits .152and 154 are illustrated in FIGURE 2 as being connected through the lowerend of the unit 10 providing fluid communication to the fluid passagespaces 44 and 56, it will be appreciated that the conduit may beintroduced from the opposite or upper end of the unit if so desired. Itwill be furthermore appreciated, that the conduit connections offered bythe pipes 152 and 154 avoid the use of flexible hosing for supplyingfluid to the pressure cavities within the cylinder assembly.Furthermore, it will be appreciated that instead of providing fluidcommunication to one end of the unit, connections to the associatedfluid handling system may be provided by conduits extending through bothchambers of the end portions of the column assembly as indicated inFIGURE 7 wherein conduits 158 and 160 are respectively mounted in thechambers 48 and 156 of the differential diameter end portions. FIGURE 7further illustrates an alternative fluid connection to the fluid passagespaces 56 and 44 through openings 162 and 164 in the cylindrical wallsof the cylinder assembly casing sections. A still further alternativearrangement may involve the mounting of the fluid handling system.components such as the pump and fluid reservoir within the axiallyspaced chambers 48, 36 and 156 of the column assembly 16.

From the foregoing description, operation and utility of thedifferential pressure operated eccentric load handling mechanism unitwill be apparent. It will therefore be appreciated, that precisionmachining and finishing of the outside diameters of the diflerentportions of the inner column assembly rather than the machining orfinishing of inside surfaces effects great economy in both manufactureof the unit and maintenance of the slide bearing surfaces thereof. Also,the section construction of the cylinder assembly enables the partialdismantling thereof without disassembly of the column structure forparts replacement and inspection purposes as hereinbefore indicatedwhich is of considerable advantage from a maintenance standpoint.Furthermore, the section construction of the cylinder assembly togetherwith the step diameter section construction of the inner column assemblymore widely accommodates a variety of different design requirements witha relatively limited number of standard size components as hereinbeforeindicated. The arrangement also inherently provides for larger eccentricload capacity by providing an intermediate bearing. Moreover, theintermediate bearing arrangement for the cylinder assembly facilitatesfield modification, welding or attachment of load carrying structurestothe casing sections without adversely affecting the operatingcharacteristics of the mechanism because of dimensional distortions.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur tothose skilled in the art, it is not desired to limit theinvention to the exact construction and operation shown and described,and accordingly all suitable modifications and equivalents may beresorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A fluid pressure load handling mechanism comprising, column meanshaving spaced slide bearing surfaces externally formed therein, tubularhousing means spaced throughout in surrounding relation to said columnmeans to define a plurality of annular pressure cavities, and aplurality of fixedly spaced side bearing assemblies operatively mountedon the housing means in sliding engagement with said bearing surfaces ofthe column means on opposite axial sides of said pressure cavitiessupporting the housing means on the column means for relative movementtherebetween, said column means including a center section having anenlarged external diameter and axial end portions of different externaldiameters less than said enlarged external diameter of the centersection, each of said center section and said end portions defining saidspaced slide bearing surfaces.

2. The combination of claim 1, including axially spaced chambers formedwithin said column means, fluid handling means mounted in said axiallyspaced chambers and fluid passage means disposed between said axiallyspaced chambers providing fluid communication between said annularpressure cavities and said fluid handling means.

3. A fluid pressure load handling mechanism comprising, variablediameter column means having spaced slide iearing surfaces externallyformed thereon, cylinder means lidably mounted on said column means anddefining a ilurality of annular pressure cavities, slide bearing assemlymeans operatively connected to the cylinder means or assembly thereof insliding relation to the column means at a plurality of fixedly spacedlocations on oppoite axial sides of said pressure cavities, said columnmeans including a center section having an enlarged exernal diameter andaxial end portions of different exterlfll diameters less than saidenlarged external diameter if the center section, each of said centersection and end lortions defining said spaced slide bearing surfaces,axially paced chambers formed within said column means, fluid iandlingmeans mounted in said axially spaced chambers vnd fluid passage meansdisposed between said axially paced chambers providing fluidcommunication between aid annular pressure cavities and said fluidhandling means, said cylinder means comprising, a pair of axially pacedcasing sections interconnected by said slide bearng assembly means, apair of end bearing assemblies, me of said bearing assemblies beingdirectly connected to me of said casing sections to define one of saidpressure :avities, and differential pressure head means interconiectingthe other end bearing assembly and casing secion to define the otherpressure cavity.

4. The combination of claim 3, wherein said slide bearng assembly meanscomprises, a pair of axially aligned mounting sleeves, leakagepreventing clamp means securng said mounting sleeves in assembledrelation and fluid viping bearing means internally mounted by themountng sleeves for engagement with a slide bearing surface of he columnmeans on opposite sides of the clamp means provide bearing support forthe cylinder means and eparate the pressure cavities thereof.

5. The combination of claim 4, wherein said clamp neans includesadjacent end clamp flanges connected to aid mounting sleeves and glandmeans disposed therebeween and in engagement with said slide bearingsurface f the column means.

6. A fluid pressure load handling mechanism comprisng, column meanshaving spaced slide bearing surfaces :xternally formed therein, tubularhousing means spaced hroughout in surrounding relation to said columnmeans 0 define a plurality of annular pressure cavities, and a )luralityof fixedly spaced slide bearing assemblies operaively mounted on thehousing means in sliding engagenent with said bearing surfaces of thecolumn means on )pposite axial sides of said pressure cavitiessupporting he housing means on the column means for relative novementtherebetween axially spaced chambers formed vithin said column means,fluid handling means mounted 11 said axially spaced chambers and fluidpassage means lisposed between said axially spaced chambers providingluid communication between said annular pressure caviies and said fluidhandling means.

7. A fluid pressure load handling mechanism comprisng, column meanshaving spaced slide bearing surfaces :xternally formed therein, tubularhousing means spaced hroughout in surrounding relation to said columnmeans 0 define a plurality of annular pressure cavities, and a yluralityof fixedly spaced slide bearing assemblies operaively mounted on thehousing means in sliding engagenent with said bearing surfaces of thecolumn means on )pposite axial sides of said pressure cavitiessupporting he housing means on the column means for relative novementtherebetween, said cylinder means comprising, l pair of axially spacedcasing sections interconnected by .aid slide bearing assembly means, apair of end bearing lssemblies, one of said bearing assemblies beingdirectly :onnected to one of said casing sections to define one of aidpressure cavities, and differential pressure head means nterconnectingthe other end bearing assembly and casng section to define the otherpressure cavity.

8. The combination of claim 7, wherein said column means includes acenter section having an enlarged external diameter and axial endportions of different external diameters less than said enlargedexternal diameter of the center section, each of said center section andend portions defining said spaced slide bearing surfaces.

9. A fluid pressure load handling mechanism comprising, column meanshaving spaced slide bearing surfaces externally formed therein, tubularhousing means spaced throughout in surrounding relation to said columnmeans to define a plurality of annular pressure cavities, and aplurality of fixedly spaced slide bearing assemblies operatively mountedon the housing means in sliding engagement with said bearing surfaces ofthe column means on opposite axial sides of said pressure cavitiessupporting the housing means on the column means for relative movementtherebetween, said slide bearing assembly means comprising, a pair ofaxially aligned mounting sleeves, leakage preventing clamp meanssecuring said mounting sleeves in assembled relation and fluid wipingbearing means internally mounted by the mounting sleeves for engagementwith a slide bearing surface of the column means on opposite sides ofthe clamp means to provide bearing support for the cylinder means andseparate the pressure cavities thereof.

10. In a fluid pressure actuating device, a tubular housing assemblyhaving opposite axial ends, a column assembly having spaced slidebearing surfaces extending through the housing assembly in radiallyspaced relation thereto, a plurality of load sustaining slide bearingsfixedly mounted by the housing assembly adjacent to and intermediatesaid opposite axial ends for movably supporting the housing assembly onthe column assembly, said slide bearings being respectively in slidingcontact with said spaced slide bearing surfaces, means defining separateaxially spaced pressure chambers between each of the slide bearings andmeans for supplying fluid under pressure to said pressure chambers.

11. In a fluid pressure actuating device, a tubular housing assemblyopen at opposite axial ends thereof, a column assembly having spacedslide bearing surfaces extending through the housing assembly radiallyspaced therefrom throughout, a plurality of fixedly spaced slidebearings mounted by the housing assembly adjacent to and intermediatesaid opposite axial ends for movably supporting the housing assembly onthe column assembly, said slide bearings being respectively in slidingcontact with said spaced slide bearing surfaces to define axially spacedpressure chambers between each of the slide bearings adjacent saidopposite axial ends and the slide bearings intermediate the axial ends,and a plurality of seal means mounted by the housing assembly at theaxial ends thereof and between the intermediate slide bearings forwiping engagement with said slide bearing surfaces on the columnassembly to pressure seal the pressure chambers.

12. The combination of claim 11 wherein the housing assembly comprisesaxially separable sections, and means for disconnectably securing saidsections together between the intermediate slide bearings to permitinspection of the slide bearing surfaces and replacement of the thoseseal means located between said intermediate slide bearings, by axialseparation of said sections.

13. In a fluid pressure actuating device, a tubular housing assemblyopen at opposite axial ends thereof, a column assembly having spacedslide bearing surfaces extending through the housing assembly radiallyspaced therefrom throughout, a plurality of fixedly spaced slidebearings mounted by the housing assembly adjacent to and intermediatesaid opposite axial ends for movably supporting the housing assembly onthe column assembly, said slide bearings being respectively in slidingcontact with said spaced slide bearing surfaces to define axially spacedpressure chambers between each of the slide bearings adjacent saidopposite axial ends and the slide bearings intermediate the axial ends,said housing assembly comprising axially separable sections, and meansfor dis connectably securing said sections together between theintermediate slide bean'ngs to permit inspection of the slide bearingsurfaces by axial separation of said sections.

14. A truck elevator comprising a cylinder surrounding a piston rod,said piston rod extending through and beyond the ends of said cylinder,a piston fixed to said rod within said cylinder, whereby said cylindermay be reciprocated along said rod, said piston defining end walls of anupper and lower chamber in said cylinder, conduit means connected to theupper chamber in said cylinder, conduit means connected to the lowerchamber in said cylinder, means associated with each of said conduitmeans for controlling the flow of hydraulic fluid through said conduitmeans, a first passage extending through said rod and opening into saidupper chamber on one side of said piston, a second passage extendingthrough said rod and opening into said lower chamber on the other sideof said piston, said passages being in communication with said conduitmeans, mounting brackets securing the ends of said rod in an uprightdisposition, said cylinder being mounted for rotation about itslongitudinal axis, load support means secured to said cylinder formovement with sadi cylinder, and said load support means including atleast one support plate extending in a direction substantiallyperpendicular to the longitudinal axis of said 2 cylinder.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent. 5UNITED STATES PATENTS 2,036,967 4/ 1936 Lundberg et a1 91-36 X 2,444,4747/ 1948' Somes et a1 92-117 A 2,474,336 6/1949 Stone -7 92-2 2,550,9255/1951 Weirnar 92-110 2,930,499 3/1960 Landen 214-75 3,134,231 5/1964McCreery 92-117 X 3,291,261 12/1966 Robb 187-9 841,649 1/1907 Howe et a1..t. 121-50 904,567 11/1908 Shevlin et a1 121-123 945,462 1/1910 Kleinet a1. 121-123 2,451,089 10/ 1948 Hunter 309-3 2,610,613 9/1952 Bryant.

2,625,115 1/ 1953 Maloney 92-169 U.S. Cl. X.R.

